During the operation of shell and tube type of nuclear steam generators having characteristic U-tube bundles, corrosion materials from the various systems tend to settle out in the steam generators. This material forms a layer on the internal components and a portion settles onto the tubesheet where it can be removed by sludge removal operations of the prior art.
Some of this material adheres to the heat exchange tubing where the thickness of this coating gradually increases and eventually degrades the heat exchange characteristics of these tubes. This material forms a scale on the tubes in some plants. Prior art attempts have been made to try to remove the material including shocking the tubes with nitrogen bubbles, varying shutdown routine, chemistry injections and high pressure lancing (spraying) as in U.S. Pat. No. 5,320,072, issued Jun. 14, 1994. None of these have been totally effective and some plants continue to see the degradation increase.